Practical design procedure of resonant snubber with current transformer and performance evaluations of a digitally controlled three phase soft switching inverter

In this paper, a high frequency transformer-assisted auxiliary active resonant commutation snubber (HFTA-ARCS) for voltage source soft switching pulse width modulated power conversion and inversion circuits using IGBTs is presented. A three phase voltage source type soft switching inverter incorporating HFTA-ARCS circuits in its three bridge legs can reduce current rating of auxiliary active power switches and has simplified sensorless control scheme for which specified boost current management for soft switching is not required. Its operation principle and digital control scheme are described and a practical design method of circuit parameters on this HFTA-ARCS circuit is also introduced on the basis of computer simulation. Moreover, this space vector modulated soft switching inverter system with DSP-based digital control scheme is discussed on the basis of performance evaluations. The effectiveness of this inverter is proved by simulation results. The operating performances of this inverter system are compared with those of conventional three-phase hard switching inverter under practical conditions of specified parameters.